WDPN32 PGTW 231500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 24W (RAGASA) WARNING NR 021//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 20.8N 116.0E
   INITIAL INTENSITY: 115 KTS
   GEOGRAPHIC REFERENCE: 135 NM SOUTHEAST OF HONG KONG
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 45 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A
WELL-DEFINED, SYMMETRICAL EYE WITH A DEVELOPING MOAT AROUND THE
EYEWALL, POTENTIALLY INDICATING A SECOND EYEWALL REPLACEMENT CYCLE.
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY REVEALS FURTHER
WEAKENING IN THE NORTHWESTERN QUADRANT, WITH ADDITIONAL WEAKENING
NOW OCCURRING ALONG THE NORTHEASTERN QUADRANT. ENVIRONMENTAL
ANALYSIS INDICATES A HIGHLY FAVORABLE ENVIRONMENT, CHARACTERIZED BY
STRONG RADIAL OUTFLOW, WARM SEA SURFACE TEMPERATURES (28-29 C), AND
LOW VERTICAL WIND SHEAR (10-15 KTS). THERE IS A STREAK OF DRY AIR
TO THE WEST OF THE STORM, HOWEVER, IT IS EXPECTED TO HAVE A
NEGLIGIBLE IMPACT ON INTENSITY. THE INITIAL INTENSITY OF 115 KTS IS
ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE WEAKENING TREND
OBSERVED IN THE AFOREMENTIONED EIR, IN ADDITION TO THE OBJECTIVE
INTENSITY AIDS AND AGENCY DVORAK FIXES LISTED BELOW. THE INITIAL
POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE WELL-DEFINED
EYE.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: THE ELONGATED SOUTHERN PERIPHERY OF THE
SUBTROPICAL RIDGE (STR) TO THE NORTHEAST


AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.5 - 127 KTS
   RJTD: T6.0 - 115 KTS
   RCTP: T6.5 - 127 KTS
   KNES: T6.0 - 115 KTS
   DEMS: T6.5 - 127 KTS
   CIMSS ADT: 117 KTS AT 231130Z
   CIMSS AIDT: 113 KTS AT 231130Z
   CIMSS D-MINT: 119 KTS AT 231204Z
   CIMSS D-PRINT: 115 KTS AT 231210Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG RADIAL

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: LOW

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TYPHOON (TY) 24W IS FORECAST TO MAINTAIN ITS
WEST-NORTHWESTWARD TRAJECTORY UNTIL LANDFALL IN SOUTHERN GUANGDONG
PROVINCE JUST AFTER TAU 24. AFTER LANDFALL, THE BUILDING STR TO THE
NORTH IS EXPECTED TO TAKE 24W ON A MORE WESTWARD TRACK. 24W WILL
THEN TRAVERSE SOUTHERN CHINA, SKIRTING THE COAST OF THE GULF OF
TONKIN AT AROUND TAU 36. AFTER TAU 36, 24W WILL TRACK INTO NORTHERN
VIETNAM AND LAOS. UNTIL LANDFALL, 24W WILL REMAIN IN A FAVORABLE
ENVIRONMENT TO MAINTAIN ITS INTENSITY, ONLY WEAKENING SLIGHTLY OVER
WATER DUE TO MODERATE SOUTHEASTERLY SHEAR (15-20 KTS). ONCE 24W IS
OVER LAND, OROGRAPHIC INTERACTION WILL CAUSE RAPID DETERIORATION,
LEADING TO DISSIPATION BY TAU 72.

MODEL DISCUSSION: JTWC NUMERICAL MODEL TRACK GUIDANCE IS IN GOOD
AGREEMENT ON A NORTHWESTWARD TRACK THROUGH TAU 24, FOLLOWED BY A
SLIGHT CURVE TO TRACK WESTWARD. THE BULK OF JTWC CONSENSUS MEMBERS
FORECAST 24W REMAINING OVER LAND OR ALONG THE COAST OF THE GULF OF
TONKIN, WITH NAVGEM AND GFS AS THE ONLY MEMBERS KEEPING 24W WELL
OFFSHORE, LENDING UNCERTAINTY TO THE TRACK FORECAST. THEREFORE, THE
JTWC TRACK IS PLACED WITH MEDIUM CONFIDENCE IN CONCURRENCE WITH THE
BULK OF CONSENSUS MEMBERS. INTENSITY GUIDANCE, ON THE OTHER HAND,
ARE IN STRONG AGREEMENT IN A SLIGHT, THOUGH CONSISTENT, WEAKENING
UNTIL LANDFALL. AFTER LANDFALL, INTENSITY GUIDANCE REMAINS IN
STRONG AGREEMENT IN 24W RAPIDLY WEAKENING UNTIL DISSIPATION AROUND
TAU 72. AS A RESULT, THE JTWC INTENSITY FORECAST IS PLACED WITH
HIGH CONFIDENCE.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: MEDIUM
   INTENSITY 00-72 HR: HIGH//
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